Aggressive behavior and violence impact both the health of individuals and American society. Aggressive behavior is highly plastic. Circulating steroids modulate aggressive behavior, as do learning processes such as reinforcement and associative learning. The proposed research is intended to integrate aggression-related learning into the field of behavioral neuroendocrinology. It is my hypothesis that surges in testosterone (T) following aggressive interactions render engaging in aggressive behavior reinforcing, and that corticosterone (CORT) released during aggression facilitates associative learning. The model organism will be the green anole lizard (Anolis carolinensis). A conditioned place preference paradigm will be used to determine whether engaging in aggression is reinforcing. Pharmacological and physiological manipulations of testosterone will then be undertaken to determine whether T surges are responsible for this reinforcement. Classical conditioning of aggressive behavior will then be used in conjunction with pharmacological manipulations of CORT to determine whether this hormone enhances aggression-related associative learning. The results of these studies will provide new information about the ways in which experience and hormones can interact to influence aggressive behavior.